Method of firing regenerative furnaces or the like



Dec. 1942. w. '7. DEN 2,3o3,62o

METHOD OF FIRING REGENERATIVE FURNACES OR THE LIKE Original Filed July :51, 1940 checker-brick or tile indicated at 1.

Patented Dec. I, 1942 METHOD OF FIRING REGENERATIVE FURNACES OR LIKE William T. Dean, Gary, Ind.

Original application July' 31,1940, Serial No.

348371. Divided and this appl cation Novembe- 23, 1940, Serial No. %6,929

2 Claims.

This inventionrelates to improvements in the method of firing soaking pit furnaces and the like, this application being a division of my pendioapplication, Serial No. 348371, filed July 31.

My invention contemplates the use of rich and lean fuels by an improved method of firing, whereby to produce a highly luminous flame and thereby eliminate the injurious effects of direct localized fiame impingement of high temperature flames upon the ingots or steel being heated.

I further have in View the use of blast furnace gas as a source of lean fuel, and combine the source with a rich fuel such a coke oven gas, in such a manner that the blast furnace gas may be utilized without costly cleaning treatment.

More particularly, it is an object of my invention to utilize a lean ,gas to modify and control a rich gas so as to obtain a luminous fiame for heating, which fiame characteristic and control is obtained without the necessity of initial admixture of the, two fuels prior to combustion.

A still further object' is toprovide for combined rich and lean'fuel combustion so related as to provide for the improved combustion and flame characteristics as above stated.

Additional objects and advantages will become apparent from the following description t'aken in connection with the accompanying drawing,

wherein:

Figure 1 is a sectional elevation of the furnace constructed under the present invention; and

Figure 2 is a diagrammatic plan of the showing of Figure 1.-

In the drawing, the furnace 2 includes firing zones 3 and 4 each comprising a lean and a rich fuel flring zone, with the wall of said furnace so constructed and'arranged as to provide adeflecting wall 5. Located at opposite sides of the tumace are regenerator chambers 6 lined with Separated from said regenerator chambers 6 by walls 8 are hot slag chambers or pockets s Positioned centrally of said furnace and between the regenerator chambers 6 are soaking pits 9 within which the steel to be treated is positioned. The bridge walls II), forming the ends of said soaking pits, extend upwardly beyond the hearth or base |2 of said pits to a point in substantial alignment with and laterally spaced from the deflecting walls& at each side of said furnace, and assist in precipitating the solids from the outflowing gases, said walls and Il) thus providing defiecting passages between the rich and lean fuel ring zones.

Extending from each regenerator chamber, as shown in dotted lines in Figure 2, isa fiue ll connecting with a branch l5 of the main flue iS leading to a stack I'I. Positioned within the main flue IS is a main damper IB controlled, in any desired manner, from the operation'station (not shown) -to regulate the amount of draft desired for said furnace. A source of air supply is connected to the pipe !9, said air being supplied by low pressure blowers (not shown) or, it desired, such air may be induced by st-ack action. A damper 20 is positioned within the air inlet pipe !9 to control, as desired, the amount of air supplied. Positioned adjacent the air outlet pipe |9 is a defiector 2l for directing the air to either regenerator chamber, as desired, while reversing dampers 22 are arranged adjacent the air outlet toadmit the directed air supply to that side .of the regenerators not connectedto the stack l'l. Dampers 3l are regulated to connect either regenerator to the stack l'l when the dampers connecting the opposite regnerator to the stack are closed. Individual dampers 23 are positioned within the fiues leading to each regenerator' chamber to regulate the amount of air supplied to the respective pits 9 or to limit the am'ount of draft thereto.

The hazard of directly impinging flames upon the surface of certain steels has led to the adoption of automatic means for reversing such furnaces on a time or temperature basis and to the use of automatically controlled combustion, or at least visual means for knowing combustion conditions with quick and accurate hand controls.

In designing new pits or furnaces, space limitations may not prevent ample allowance for regenerative chambers but, in order to convert existing furnaces to the use of lean gases requirlng approximately double the flue area with increased heating surface, space is not always available for the larger regenerators required by present designs for regenerator checkers.

Therefore, the present invention contemplates the burning of combinations of rich and lean gases by giving to each fuel the combustion space and time elements needed for .the best results. Separate fuel supply pipes are provided for the 'rich and lean fuel ring zones, 29 diagrammatically indicating the pipes for rich fuels and 30 the pipes for lean fuels. In each case, suitable nozzles are used to impart a wide angle diffusing shape to the rich mixture and a narrower whirling mixing cone to the lean mixture With said bridge wall o to insure complete mixing. Upon r revcrsing the flow, the products of combustion leave the pit horizontally and are defiected downwardly by said deflecting wall through the passages between the rich and lean gas firing zones, thence again horlzontally to one of the regenerators. This change in direction with the change in velocity tends to throw down practically all of the entrained solids into a hot slag pocket or chamber 8 beneath the defiecting passage. The hot gases then enter the regenerator flues substantially free from solids or slag, greatly increasing the life of the upper courses of checkers, at present so susceptible to slag damage.

In practicing the present method, a ean fuel, such as blast furnace gas is supplied to the gas pipes 30 at the side of the furnace being fired,

said gas mixing with the incoming air from the.

preheated regenerator chamber 6 therebelow to effect substantially complete combustion of said gas. The impingement of the burning gases upon the bridge wall o aids combustion through aiding the mixture of gas and air, and effects a separation of the -entrained solids from the gas, which solids lose' their velocity and fall into the slag pocket 8 below said wall.

The burning blast furnace or lean gas is alsodeflected upwardly by the wall !0, between said wall and the defiection wall 5, and engages the stream of rich gas'from the bumer 29 spaced thereabove. At the zone of engagement of the said gases. the temperature of the combusted mixture of air and lean gas is high in relation to that of the rich gases, whereupon the following action takes place.

Due to the utilization of the incoming air for burning the lean gas, there exists a shortage of air for the combustion of the rich gas which readily permits a partial decomposition of the incompletely combusted rich gas.

- The high temperature of the lean gas and air combustion cracks the incompletely combusted rich coke oven or other high hydrocarbon gas, liberating free carbon from the latter, whereupon the heating flame reaching the hearth and the ingots is rendered highly luminous and soft, and

has an increased area of spread or dispersion over the hearth.

The resulting flame will not injure the steel ot the ingots as the same does not have the high embodiment of the invention, it will be understood that I do not wish to be limited exactly thereto, since various modiflcations may be made without departing from the scope of the invention, as deflned in the appended claims.

I claim:

1. The herein described method of ring a regenerative furnace or the like having a soaking pit, which consists in initiallv burning a lean gas to substantially complete combustion with substantially all of the air supply from a hot regenerator of said furnace, burning a rich gas in incomplete combustion in spaced relation to the initial combustion of the lean gas, mixing the products oi' the lean gas combustion with the burning rich gas adjacent the soaking pit, thereby increasing the temperature of th resulting mixture in sufiicient amount to crack the incom- `pletely combusted rich gas to produce a luminous heating flame' in said pit.

2. The herein described method of firing a regenerative furnace or the like having a soaking pit, which consists in initially burning 'a blast furnace gas to substantially complete combustion with substantially all of the air supply from a. hot regenerator of said furnace, burning a rich gas in incomplete combustion in spaced relation to the im'tial combustion of the blast furnace gas, mixing the products of the blast furnace gas combustion with the burning rich gas adjacent the soaking pit, thereby increasing the temperature of the resulting mixture in suflicient amount to i crack the incompletely combusted rich gas to produce a luminous heating flame in said pit.

WILLIAM T. DEAN. 

